1. Technical Field
This invention relates to a communication device, a communication system, and a computer readable medium.
2. Related Art
An IP facsimile machine for conducting digital communications of image information using an Internet protocol exists. Some IP facsimile machines can conduct not only digital communications of image information using the Internet protocol, but also analog communications of image information via a public telephone switch line. Such an IP facsimile machine includes not only a communication interface compatible with the Internet protocol such as a LAN card, but also a communication interface compatible with the public telephone switch line such as analog facsimile communication card.
In recent years, communications have been conducted between facsimile machines using a next generation network (NGN) of a base network for providing new information communication service in which fixed communications and mobile communications are merged and telephone, data communications, and streaming broadcast are merged. A repeater such as a home gateway device may be used as a device for relaying communications between the next generation network and the IP facsimile machine.
When a repeater such as a home gateway device relays communications between the next generation network and the IP facsimile machine, generally an optical fiber connected to the next generation network is connected to the corresponding port of the repeater. A LAN cable connected to a LAN card included by the IP facsimile machine and a modular cable connected to an analog facsimile communication card included by the IP facsimile machine are connected to the corresponding ports of the repeater. When analog communications are conducted between the IP facsimile machines, analog-digital conversion and digital-analog conversion are performed in the repeater.
When a communication start request according to the Internet protocol (for example, INVITE request in SIP (Session Initiation Protocol)) is transmitted from an IP facsimile machine to an associated IP facsimile machine via the next generation network, one repeater places the start request in all ports of the repeater as an incoming call and transmits a response determined by executing arbitration processing among responses when the responses from all ports are complete (for example, response determined based on predetermined priority) to the IP facsimile machine transmitting the start request.
When the communication start request is transmitted to the associated IP facsimile machine while the associated IP facsimile machine is communicating with another facsimile machine, arbitration processing is performed between a response indicating communicating from the LAN port of the repeater (for example, 486 response in SIP) and a response indicating communication rejection from the analog port of the repeater (for example, 488 response in SIP), whereby the response indicating communication rejection (for example, 488 response in SIP) may be transmitted to the IP facsimile machine transmitting the start request.